Question

Describe how the distribution of blood is regulated to accommodate tissue needs.

- through Sympathetic NS

- through Local control by paracrine signals

Answer 1

1) through sympathetic ns -

i) cardiac innervation -

Sympathetic supplu to the heart is by the sympathetic nerve cells which lie in the intermediolateral horn of the spinal cord extending from T1-T5 vertebra to supply sa node , av node and muscles of atria and ventricles.

Stimulation of sympathetic fibers cause:

Increase in heart rate, force of contraction , conductivity in conduction tissue which results in the rapid blood flow to the tissue .

ii) Peripheral vascular innervation :

Nerves arise from the cell bodies in the intermediolateral horns of spinal cord extending fromT1-L2 spinal segments .

The innervated regions includes arterioles, metarterioles, precapillary sphincter .

This system increases the peripheral resistance which results in decrease blood flow to the tissue from heart. Heart has to exert more pressure to supply the tissues .

2) through local control by paracrine signaling :

Tissues has capacity to regulate their own blood flow.

Some metabolites released locally from the cells results in increased tissue activity thus producing vasodilation are the local vasodilator metabolites which includes :

Latic acid, adenosine , kinins

Whereas local vasoconstrictors produces vasoconstriction by increasing the activity of pacemaker cells which includes:-

Histamine, catacholamines.